Influence of land transformations on the hydrodynamics of the Pampeano–Puelche Aquifer System: A spatiotemporal analysis in Gran La Plata, Argentina (1991–2023)

Abstract

Urban expansion and agricultural intensification can reduce diffuse recharge, concentrate groundwater demand, and reshape hydraulic gradients in multilayer aquifer systems. This study assesses land-use/land-cover (LULC) transformations and hydrodynamic changes in the Pampeano–Puelche Aquifer System beneath Gran La Plata, Argentina (1991–2023). Methods integrated Landsat-based LULC mapping (1991/2003/2023) and kriged piezometric surfaces validated by leave-one-out cross-validation. Transition-specific spatial associations weretested using bivariate Moran's I and Local Indicators of Spatial Association (LISA), and hydroclimatic context was assessed via the 12-month Standardized Precipitation–Evapotranspiration Index (SPEI-12). Results show that grasslands declined from 36.7% to 20.9%, while urban land reached 26.2%, and greenhouse cultivation increased sevenfold. Mean hydraulic head declined by 5.9 m, and drawdown rates accelerated 5.4-fold, from 􀀀 0.05 m yr􀀀 1 (1991–2003) to 􀀀 0.27 m yr􀀀 1 (2003–2023). Net decline affected 89% of the area, with negative heads (<0 m a.s.l.) across 36%. Spatial statistics indicate that areas of greater drawdown cluster spatially with conversions from grasslands to low-density urban (I = 0.27), greenhouses (I = 0.18), and croplands (I = 􀀀 0.14), whereas riparian vegetation persistence was associated with piezometric stability (I = +0.48). Hydroclimatic conditions became drier after 2003, with mean SPEI-12 shifting from +0.26 (mildly wet) to 0.45 (mildly dry). However, the dual-apex depression cone remained spatially aligned with LULC-transition hotspots, indicating land transformation as a key spatial organizer of depletion. These findings support sustainable groundwater governance through protection of recharge and riparian corridors, infiltration performance standards for new developments, and prioritized monitoring, metering, and volumetric caps in transition hotspot areas. The workflow is transferable to data-scarce, urbanizing coastal plains requiring integrated indicators for groundwater management and regulation.